Field of the invention
The present invention concerns a front suspension device comprising a lateral arm device, for supporting and steering a motorcycle front wheel, the said arm being adapted to turn about a steering axis which is substantially orthogonal to that of the wheel and which is located substantially in the median longitudinal plane of the motorcycle.
The suspension of a body or a chassis of a vehicle on a steering wheel should, in order to maintain correct riding qualities for this vehicle, be independent from that of the other wheel(s) but this requirement means that the connections between said wheel and the suspension means are consequently much more complex. A considerable simplification was brought to suspensions cooperating with vehicle front wheels in the type of suspension called Mac Pherson suspension and described, for example, in French patent No. 1 156 145. In this type of suspension, which has since been improved, the spindle of the front wheel is carried by a shock absorber tube connected by a link hinged to the central part of the chassis and the vehicle body rests, while extruding from a relatively high bearing position, directly on a helical spring interposed between a bearing shoulder of the shock absorber tube and a bearing plate of the body.
This front suspension structure, that has since revealed to be so compact and economic that a large number of automobiles built throughout the world have been equipped with it, has never however been successfully applied to motorcycles the front wheel of which must be maintained in an accurately centered manner in the symmetry plane of the wheel, contrarily to four-wheel automobiles which can easily tolerate a cantilevered mounting of the wheel spindle.
One of the objects of the present invention is thus to provide an advantageous application to motorcycles and similar vehicles of the "Mac Pherson" type suspension in order to produce a motorcycle front suspension which is more compact, more efficient, more economic and in ge results in an improved road holding and aesthetic properties of such motorcycles and other two-wheel or three-wheel vehicles and single wheel vehicles.
With this object, the lateral arm is connected at its upper end to a suspension and/or shock absorbing block having a telescopic cylinder structure, the internal movable rod of which is hinged at its high end onto a front peak of the chassis of the vehicle, said lateral arm comprising, on the one hand, a "C"-shpped part which encases a portion of the cross-section of the periphery of the wheel and, on the other hand, a lowe carrying the axle of the wheel and which is provided with a ball and socket articulation of which the center of rotation is located substantially in alignment with the steering axle and which cooperates with an associated ball and socket articulation piece mounted at the end of a connecting arm which is in turn rotatively mounted on an axis of the chassis of the motor cycle perpendicularly to the median plane of the motorcycle, in order to ensure lateral guiding of the lateral arm.
According to a first embodiment of the invention, the "C"-shaped part of the lateral arm is connected by a ball and socket articulation to a steering link adapted angularly to orientate the wheel by rotation of the support arm and of the telescopic block the movable rod of which is integral in rotation with the front peak of the chassis, so as to be subjected to the frictional torque exerted by the relative rotation of the telescopic block with respect to the movable rod and to an associated shock absorbing piston or similar associated elements rotationally integral therewith.
According to another embodiment of the steering control means the movable rod is axially supported on the front peak of the chassis of the motorcycle through which it extends so as to be free to rotate therein, while being axially movable inside the telescopic block with which it is integral in rotation, that part of the said movable rod which extends above the front peak being rendered integral with a handlebar provided with two handles for the direct steering control of the front wheel.
The support arm advantageously comprises adjacent to the axle of the wheel an extension directed towards the rim of the wheel and the telescopic block and on which is fixed by appropriate means, such as screws, at least one brake disk yoke surrounding a brake disk rendered integral at least in rotation with the rotating axle of the wheel.
According to another embodiment concerning the rotatively members, the axle of the wheel is rotatively mounted inside the support arm through the intermediary of at least one bearing axially immobilized by stop means in a bore of the support arm and protruding from the side opposite the support arm by a grooved or equivalent attachment part adapted to be rendered integral in rotation with the brake disk and the rim of the front wheel, this attachment part being extended by a threaded part receiving a rapid tightening nut fixing the wheel and the brake disk, so as to allow rapid changing of the front wheel and, where necessary, of the brake disk after shifting of the disk brake yoke(s).
According to yet a further embodiment, the ball and socket joint support which cooperates with the connecting arm is constituted by a lower axle integral with the support arm and protruding in the steering of the rolling path of the front wheel, its axis being placed substantially in the median plane of the front wheel, a ring or ball body being disposed on this lower axle and hinged on the associated end of the connecting arm, at least the rod and a part of the ring or ball body of the associated end of the connecting arm being housed inside the cup of the brake disk.
According to one feature of the invention, ensuring improved guiding, the external movable rod of the telescopic cylinder structure is hinged onto the front peak of the chassis of the motorcycle through the intermediary of a rod the axis of which is orthogonal to the median plane of the motorcycle and which is integral with the front peak and is rotationally mounted in a boring provided in an articulation head connected, possibly in an adjustable manner, to the movable rod.
According to one advantageous embodiment, the associated ball and socket articulation piece is adjustably mounted at the end of the connecting arm so as to allow adjustment of the "rake" of the front wheel of the motorcycle. This adjustable connection between the end of the connecting arm and the associated ball and socket articulation piece can be a sliding connection controlled by a jack servo-controlled by means reacting to the speed of the motorcycle, so as to cause to vary the rake of the front wheel as a function of said speed.
According to another embodiment, the suspension and shock absorbing block comprises a helical spring having a generally cylindrical or frustoconical form and the longitudinal axis of which, while being substantially located in the median plane of the motorcycle is off-centered with respect to the axis of the telescopic cylinder structure due to its off- centered position with respect to said axis of at least one of the resting cups or plates cooperating with the end of this spring, so as to apply on the lateral arm a return torque towards the straight line position.
The present invention further applies to a device comprising a lateral front suspension arm for supporting and steering a wheel and to a steering control device associated thereto, especially for a motorcycle front wheel carried by at least one support arm connected at its upper end to a suspension and/or shock-absorbing block the external movable rod of which is articulated at its end on a front peak of the chassis of the motorcycle comprising the above front suspension device.
It has already been proposed to produce a motorcycle front suspension comprising a single support arm of the front wheel which is mounted cantilevered on this arm and wherein a suspension spring is interposed between a front peak of the motorcycle chassis and the support arm by means of a movable rod of a suspension arm which is pivotally mounted on this peak. These motorcycle suspensions of the Mac Pherson type give rise to a problem regarding the connection between the steering handlebar and the single support arm of the front wheel.
In order to ensure the connection between the single support arm and the handlebar, it has been proposed to use a universal joint transmission by links that has revealed relatively expensive and complicated to manufacture, while nevertheless transmitting to the handlebar the sudden reactions due to the displacements of the suspension. Another solution consists in interlocking at least for translational motion the end of the movable rod to the handlebar and in interlocking for rotational motion through a sliding connection this rod to the telescopic suspension block body, this body being rigidly fixed to the single suspension arm. This apparently satisfactory solution has revealed in practice to be very difficult to carry out since there exists no telescopic suspension and shock-absorbing block the rod of which is interlocked in rotational motion with the block body; indeed, such an arrangement would require a sleeve integral with the rod and surrounds the block body while being coupled thereto for rotational motion by grooves, so as not to disturb the hydraulic liquid sealing means of the shock absorber.
One particular object of the present invention is to propose a device comprising a single lateral suspension arm and steering control means adapted to this Mac Pherson type suspension, which are a simple in design, do not transmit stray reactions to the handlebar while allowing to use for the constructing suspension and shock-absorbing block commercially available elements of which the reliability and economy are well established.
With this purpose in view, the suspension spring and/or shock absorbing block is a helical spring of which at least one of the end bearing planes comprises a low friction abutment allowing the spring to rotate freely about its longitudinal axis during its displacemetns and the steering control means is constituted by a handlebar or wheel rotatively mounted on a vertical axis of the said peak rotatively mounted on an axis substantially perpendicular to the median plane of the front wheel, i.e. to the steering plane, at the upper end of at least one upper link inclined towards the front of the motorcycle from its upper end and the lower end of which is also mounted on the lateral arm or support arm for rotation about an axis substantially perpendicular to the said steering plane at the upper end of at least one lower link inclined towards the front of the motorcycle from its lower end which is rotationally connected to an axis substantially perpendicular to the said steering plane, so that the upper and lower links connected in rotation respectively to the handlebar and to the support arm are pivotally interconnected in a scissor-like manner during the displacements of the front wheel suspension of the motorcycle.
According to the most current embodiment, the upper link and the lower link present substantially the same length and their respective median lines each form, in maximal extension position of the suspension block, an angle of about 30.degree. with the longitudinal axis of this suspension block.
The upper link and the lower link can present substantially different lengths and their respective median lines thus form, in maximal extension position of the suspension block, an angle smaller than 30.degree. with the longitudinal axis of this suspension block. The upper link can also present a length substantially smaller than that of the lower link so as to increase the distance between the front wheel and the axis of articulation interconnecting between the two links. The axis of articulation of the upper link is preferably substantially coaxial to the axis of articulation of the external movable rod of the suspension and shock absorbing block on the front peak of the chassis of the motorcycle.
According to another very compact embodiment of the invention, the upper link presents, on its upper part, a fork with two legs, each of which is rotationally connected to a boss of an arm of the handlebar and has at its lower part, a single central bearing through which extends a pin or assembly shaft and which is disposed between two bearings that are also crossed through by the assembling pin and which are both provided at each of the ends of the legs of a fork of the lower link, two lower legs of which extend therefrom are rotationally connected each to a corresponding boss provided on the support arm. The corresponding upper and lower links present the general form of a trapezium the large base of which is articulated respectively to the handlebar and to the support arm of the front wheel, and the small bases of which are joined to each other in the zone crossed through by the assembly pin and are articulated or hinged to each other.
According to another embodiment of the invention, the rotation connection of the upper end of the upper link and that of the lower end of the lower link are located beyond the bearing planes of the ends of a helical spring constituting the suspension spring of the suspension block. The steering links thus constitute supplementary guiding means of the suspension block during its displacements.